171 174 codes need some help

I had a new lower manifold installed, mechanic said he did new gasket set and bolts. I replaced dpfe sensor, cleaned iac, new pcv valve. I did noticed IMRC rod not attached. will the rod cause the lean code? my gasket set part is #ms959852, but now i am wondering if he replaced the bolts or not. can just bolts be done or is that a major job

A IMRC rod could cause the code as you have more air available to 1 bank of cylinders than the other.
I am guessing that you have a 1999 or newer Windstar?....as these are the ones that get the new isolator bolts for the upper intake manifold.
P0171 / P0174 are tough codes to track down.....usually a vaccum leak.
A vaccum leak is any air entering the intake at a point that is past the MAF......the flex hose, intake manifold, any vaccum line......etc
Look around for any vaccum line that is not connected.
The breather line that goes from the flex hose to the rear valve cover (1999 and newer) and any other line that could have been bumped or forgotten when the upper intake manifold was off.
They connect to the back side.....where you cannot really see them.

all this work was done after the cel came on, the cel has actually been on for about 5 years now. the first year it came on i brought it to 2 mechanics and they told me its like searching for a needle in a haystack with the windstar and told me i would be wasting my money for them to trouble shoot it. yes i have a 2000 winstar 3.8L. how many vac. lines are there? is there a way i can see the bolts and possibly change them without getting into too much other work. would clogged egr ports do the lean codes.

There are many mysteries in our world, but finding the lean codes on the Winny ain't two of them!

Yes, the EGR jets ... some being plugged, some not... will cause an unbalance of combustion air in some cyls ... I.e, lean codes. Even the EGR valve and its control components can cause some problems. A poorly working/dirty MAF sensor can cause grief ....

.... but most likely it is a vacuum leak. Hoses, splits in air intake passageway to throttle body, gaskets around the air intake manifold, splits in air intake plastic parts .... and likely the infamous isolator bolts.

The IMRC rod seal? Unlikely I would guess .... but a smear of hi-temp grease applied will answer the question. The IMRC links? Hardly a chance.
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With a new set of gaskets for intake manifold and islolator bolts ... perhaps a new MAF sensor, in hand ... I would bet a big pig that novice-me could find/fix the problem in 4 hrs.

i had a lower manifold put in and was told i would get new gaskets and iso bolts( hope he did) the manifold was a used part not sure if he cleaned the egr ports or not i would think a reputible mechanic would since they get paid by the hour, but who knows. i think i may need to open the upper plenum to see bolts and check egr ports. is it easy to open the upper plenum, are there a lot of connections to fool with. i am not a mechanic but not a moron either. what are some common lines and could check for leaks and how do i tell